Expansions of conservation areas such as the Natura 2000 network should be done in a way that improves not only area coverage but also representation (Visconti et al. 2019). The MTA indicator is one way of assessing this using information of species distributions covered by conservation areas.
The calculation of the MTA indicator (defined by Jantke et al. (2019) ) used EEA species and habitat reporting data and Natura 2000 information. For each 10 x 10 km grid id in the EEA Reference grid, we estimated the cumulative coverage of Natura 2000 sites per time frame, which we identified from the date SPAs, SCIs or SACs were designated or first added to the database. We then summarized per species or habitat the total distribution as well as the coverage of Natura 2000 sites within their distribution. See also the Section 2 section for a more detailed methodology breakdown.
The current calculation of the MTA is feasible every 6 years and can also be further refined to account for land-cover and land-use change, for example using data from the Corine Accounting layer. Furthermore, for comparability data on EEA reporting is used, although more higher resolved species distribution data (such as those produced by the NaturaConnect project) are slowly becoming available.

As data sources we relied for this demonstration on the officially used Article 12 (‘Birds directive’) and Article 17 (‘Habitats directive’) reporting data. Sensitive species were also included in those calculations.

As conservation areas we relied on the Natura2000 geopackage (last updated in April 2024).

Targets were calculated as log-linear targets (following (Rodrigues et al. 2004)) with a lower bound to 20% and upper bound to 90%. Different target formulations are feasible, for example those minimizing species-extinction risk (following (Jung et al. 2021)) and should ideally be based on a scientifically sound process at EU Member state level that takes into account ecological features and conservation needs.